This invention relates generally to improved contact lens cleaning and conditioning solutions for removing and inhibiting build-up of tear film deposits and debris on lens surfaces.
In addition to the foregoing, the solutions of the present invention have improved versatility in being adaptable for most contact lens cleaning processes ranging from room temperature cleaning to high temperature disinfecting without adversely affecting the physical characteristics of the lenses.
When contact lenses are removed from the eyes, they lose water and retain on their surface a deposit or proteinaceous oily and sebaceous matter which, if not removed, greatly reduces wettability properties and optical clarity of the lenses. In the case of hard contact lenses fabricated from poly(methyl methacrylate), they are of such firmness the lenses can be treated with mechanical devices to remove deposits of contamination from their surfaces. Likewise, because hard contact lenses do not absorb appreciable amounts of water, the selection of cleaning agents is relatively non-critical. In many instances, use of even harsh disinfecting and cleaning agents on hard contact lenses does not create a problem.
However, because of the hydrophilic properties of soft contact lenses formulated from materials like poly(hydroxyethyl methacrylate), they do absorb more water than hard contact lenses. Consequently, greater care must be exercised in formulating cleansing solutions for soft contact lenses because materials in the solutions can be absorbed and concentrated in the lenses which in-turn can damage the lens and even injure the eyes of the user.
In many instances, solutions intended for hard contact lenses are generally not adaptable for use with soft contact lenses. This may be illustrated, for instance, in the case of hard contact lens solutions containing benzalkonium chloride or chlorobutanol, if used on soft contact lenses their important hydrophilic properties may be lost. Thus, in formulating contact lens care solutions, such as cleaning compositions, a number of factors need to be carefully weighed to assure total compatibility of the system in terms of functional efficaciousness, potential for damage to the lens and possible hazards to the wearer's eyes.
Various contact lens care formulations have been described in the literature, including the following patents: U.S. Pat. Nos. 4,323,467; 3,882,036; 3,954,644; 3,884,826; 4,127,423. U.S. Pat. No. 4,323,467 to Fu discloses an all-purpose type solution for storing, cleaning or wetting contact lenses containing a poly(oxyethylene)-poly(oxypropylene) substituted ethylene diamine surfactant having a molecular weight of between 1600 and 27,000; a germicidal agent; a viscosity builder; a tonicity agent and sequestering agent. Fu suggests, in essence, that any member of the family of surfactants, available from BASF-Wyandotte under the registered trademark Tetronic, may be employed in contact lens care solutions. However, little, if any, information is provided identifying which specific surfactants within the broad class may be used at the lowest concentration to assure optimal cleaning efficiencies and lens compatibility while minimizing the potential for eye irritation. Non-irritating amounts of surfactant up to as high as 40 percent by weight are recommended. It is also significant that viscosity builders are required by the patentee to maintain a film of surfactant on the surface of the lens for enhanced comfort and wearability. However, it was discovered that viscosity builders have the disadvantage of making the lens cleaning process more difficult. Because of increased adherence, the cleaning compositions resist removal during final washing, increasing the risk of residue build-up and incidence of eye tissue irritation.
U.S. Pat. Nos. 3,882,036 and 3,954,644 to Krezanoski et al also suggest all-purpose type care solutions for contact lenses containing poly(oxyethylene)-poly(oxypropylene) block copolymer surfactants available under the registered trademark Pluronic. These surfactants are not adducts of ethylene diamine.
U.S. Pat. No. 3,884,826 to Phares et al disclose a gel type cleaner for hard contact lenses containing various non-ionic surfactants commercially available under well-known trademarks, like Tweens, Spans, Myrj, Brij, Pluronics, etc. These non-ionic cleaners, however, do not provide the capability of wide temperature range cleaning needed for removal of tear film buildup on lenses or prophylactic conditioning of lenses.
As in a number of the foregoing patent publications, U.S. Pat. No. 4,127,423 to Rankin discloses contact lens cleaning solutions also containing inter-alia non-ionic surfactant, such as Pluronics, along with tonicity agents, viscosity agents, detergents and bactericides. Such additives will not increase the cleaning efficiency spectrum of surfactant based contact lens cleaners, and may only compound lens compatibility problems and possible risk of materials being absorbed and concentrated in the lenses increasing the risk of eye irritation. Accordingly, there is a need for improved cleaning and conditioning solutions which are efficient in removing proteinaceous and lipid tear-film build-up and also control the rate of subsequent film development while being compatible with both soft and hard contact-lenses, and perform effectively under most cleaning process conditions.
The present invention provides an improved means for both removing and inhibiting the natural build-up of film development on contact lenses, and is particularly compatible with soft type contact lenses while minimizing both the potential risk of damage to lenses and the occurrence of eye irritation. The cleaning solutiosn are specially noteworthy in they are exceptionally efficient in dispersing proteinaceous and lipid-containing tear film deposits effectively at wide temperature ranges making them readily adaptable to virtually any cleaning process.